In a power device, the power consumption is ordinary. For an improvement on the electric performance and heat dissipation of the power device, the metal electrode of the device is partially exposed from a plastic package material covering a semiconductor chip. For example, US patent application US2003/0132531A1 shows a semiconductor packaging structure 24 including a semiconductor chip with exposed bottom electrode and being used for supporting surface mounting technology. As shown in FIG. 1, a power chip MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) 10 is arranged in an interior space of a metal can 12. A drain electrode at one side of MOSFET 10 is attached on the bottom of the metal can 12 in the interior space via a conductive silver paste 14 so that the drain electrode is electrically connected to a protruded edge 22 of the metal can 12; while a source electrode and a gate electrode at an opposite side of the MOSFET 10 are co-planar with the upper surface of the protruded edge 22. A low-stress and high-adhesive epoxy 16 is filled in a gap between the MOSFET 10 and the metal can 12. Although the heat dissipation issues have been solved for the packaging structure 24, it is expensive to produce such metal can 12. In addition, both the source electrode 18 and the gate electrode are fixed on the semiconductor chip 10, thus it is difficult to adjust the gate electrode and the source electrode 18 to be flush with the upper surface of the protruded edge 22 as such it is difficult to attach the power device 24 on a bonding pad on a PCB (Printed Circuit Board). Furthermore, the thickness of different semiconductor chips 10 will be varied and the above-mentioned problems are more troublesome.